1. Field of the Invention
The present invention relates to circuit testing devices and methods and, more particularly, to such devices and methods for high-density circuits, test pin arrays, and multiple-row ball grid arrays.
2. Description of Related Art
Test probes for use in testing electronic circuitry are known in the art to comprise one or more elongated arms having a downwardly depending, typically pointed, electrically conductive distal tip for contacting a portion of the circuit. The inventor of the present application has disclosed test probes and assemblies in U.S. Pat. Nos. 4,151,465; 4,177,425; 4,618,821; and 6,489,795, the contents of which are incorporated herein by reference.
It is known to be preferable for the probe arm to have a certain amount of flexibility for permitting reproducible and nondamaging contact with the circuit. Exemplary flexure means are disclosed in the ""465 and ""821 patents. Other such probes are disclosed in U.S. Pat. Nos. 4,973,903; 4,965,865; 5,720,098; and 5,883,519.
The present invention is directed to a test probe for testing microcircuits. The test probe comprises a torsion head blade contact that provides a capability of fabricating probe assemblies and test sockets capable of probing high-density circuits, test pin arrays, or multi-row ball grid arrays.
The probe for testing circuits of the present invention has improved flexibility and has a longer lifespan and durability. The test probe comprises a first and a second elongated, generally planar, electrically conductive arm member. Each of the first and the second arm members have a pair of generally planar and parallel side surfaces extending along a longitudinal axis in a first plane. A front portion has an elongated slot extending through the arm between the side surfaces and comprises a downwardly extending tip terminating in a probe end for contacting a circuit to be tested. The tip of the first arm member is shorter than the tip of the second arm member.
A rear portion of each arm member is movably affixable to a retaining block. A central portion positioned between the front portion and the rear portion comprises means for connecting to a test circuit.
The first and the second arm members are relatively positioned in commonly oriented fashion with the second arm member above and generally coplanar with the first arm member in the first plane. The probe ends of the first and the second arm members are generally coplanar in a second plane generally perpendicular to the first plane.
Typically the test probe is part of an assembly comprising a first plurality of such test probes, affixed in stacked relation in a retaining block, and a second plurality of such test probes, affixed in stacked relation in the retaining block in opposite orientation to the first plurality.
The test probe of the present invention allows for two electrically isolated probes to be placed side by side, allowing for two probes to be placed on each pad or solder ball for true Kelvin probing, for example. Multiple Kelvin probes are then usable in-line in a single block probe assembly. Multiple probes, each electrically isolated from each other, can be positioned in a unitary retainer block.
The features that characterize the invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description used in conjunction with the accompanying drawing. It is to be expressly understood that the drawing is for the purpose of illustration and description and is not intended as a definition of the limits of the invention. These and other objects attained, and advantages offered, by the present invention will become more fully apparent as the description that now follows is read in conjunction with the accompanying drawing.